Battery cell, battery module, and method for manufacturing battery cell

Abstract

The present invention relates to a battery cell having improved durability and lifespan, a manufacturing method of the battery cell, and a battery module including the battery cell. Specifically, the battery cell includes a cell case having an accommodation space, an electrode assembly accommodated in the accommodation space and including a plurality of electrodes, electrode tabs formed on at least one side of each of the plurality of electrodes, and a separator interposed between the plurality of electrodes, a gel electrolyte containing a first lithium salt of a first molar concentration and accommodated in the accommodation space surrounding the electrode tabs, and a liquid electrolyte containing a second lithium salt of a second molar concentration lower than the first molar concentration and accommodated between the plurality of electrodes.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application Nos. 10-2022-0027003 and 10-2022-0027007, filed March 2, 2022, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a battery cell, a battery module, and a method for manufacturing a battery cell, which improves the durability and life of the battery. [Background technology]

[0003] Currently commercially available secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium secondary batteries. Among these, lithium secondary batteries have almost no memory effect compared to nickel-based secondary batteries, allowing for free charging and discharging. Furthermore, lithium secondary batteries have attracted attention due to their extremely low self-discharge rate and high energy density.

[0004] Lithium secondary batteries typically use lithium-based oxides and carbon materials as the positive and negative electrode active materials, respectively. The lithium secondary battery includes an electrode assembly in which a positive electrode plate and a negative electrode plate, each coated with a positive electrode active material and a negative electrode active material, are disposed with a separator interposed therebetween, and an exterior case that hermetically houses the electrode assembly together with an electrolyte.

[0005] Generally, lithium secondary batteries can be classified into can-type secondary batteries and pouch-type secondary batteries depending on the type of exterior material. Can-type secondary batteries have an electrode assembly housed in a metal can, while pouch-type secondary batteries have an electrode assembly housed in an aluminum laminated sheet pouch.

[0006] In recent years, secondary batteries have been widely used not only in small devices such as portable electronic devices but also in medium- to large-sized devices such as power storage devices in automobiles and power plants. When used in such medium- to large-sized devices, multiple battery cells are electrically connected to increase capacity and output. In particular, pouch-type battery cells, which are easy to stack, are often used in such medium- to large-sized devices. Here, a pouch-type battery cell refers to a battery cell in which an electrode assembly is housed in a pouch-type case made of a flexible polymer material with an irregular shape.

[0007] The pouch sheet, which is the case of the pouch-type battery cell, is made of a soft material and includes a protrusion on one side that forms a receiving space for receiving the electrode assembly, and an injection part on the other side that is open and allows electrolyte to be injected.

[0008] The electrode assembly may include a positive electrode having a positive electrode active material layer formed on a positive electrode current collector, a negative electrode having a negative electrode active material layer formed on a negative electrode current collector, a separator interposed between the positive electrode and the negative electrode, and an electrolyte.

[0009] Meanwhile, the metal foils used for the positive and negative electrode current collectors each have an electrode tab formed on at least one side. The electrode tab has a folded shape during the welding process with the electrode lead. However, because such electrode tabs are very thin and have relatively low mechanical rigidity, the electrode tabs can easily break when the folded shape of the electrode tab is repeatedly folded and unfolded or when subjected to external impact. Furthermore, the electrode tabs can corrode due to some lithium salts contained in the electrolyte during charging and discharging, and if this corrosion continues, the electrode tabs can also break.

[0010] Such disconnection of the electrode tabs leads to the inactivation of the electrodes connected to the electrode tabs, which causes the "sudden death" of the battery cell and significantly reduces the charge / discharge performance and lifespan characteristics. In particular, in the case of secondary batteries installed in automobile packs, which are exposed to frequent vibrations and impacts, disconnection of the electrode tabs may occur more frequently, which rapidly shortens the lifespan of the battery cell.

[0011] In recent years, as the thickness of current collectors has been made thinner to increase the energy density of battery cells, the mechanical rigidity of electrode tabs has also decreased, resulting in frequent breakage of the electrode tabs at bent portions or at connection portions between the electrode tabs and the electrodes. Furthermore, as battery cells become smaller, the width and length of electrode tabs become narrower, which increases the likelihood of electrode tab breakage when the battery cell is subjected to external impact. Therefore, there is a need to develop a method for preventing breakage of the electrode tabs due to external impact or electrolyte, etc., and improving the performance and service life of the battery cell. Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention has been made to solve the above problems, and aims to provide a battery cell that improves the durability and lifespan of the battery by disposing a gel electrolyte with low fluidity around the electrode tabs to prevent disconnection due to the flow and deformation of the electrode tabs, and by disposing a liquid electrolyte with high wettability around the electrode assembly excluding the area around the electrode tabs to increase the wettability of the electrolyte solution to the electrode assembly.

[0013] Another object of the present invention is to provide a battery module including the battery cell. Another object of the present invention is to provide a method for manufacturing the battery cell. [Means for solving the problem]

[0014] According to one embodiment, the present invention provides a battery comprising: a cell case having a storage space; an electrode assembly accommodated in the accommodating space, the electrode assembly including a plurality of electrodes, electrode tabs formed on at least one side of each of the plurality of electrodes, and separators interposed between the plurality of electrodes; a gel electrolyte containing a first lithium salt at a first molar concentration and accommodated in the accommodation space surrounding the electrode tab; a liquid electrolyte contained between the plurality of electrodes, the liquid electrolyte containing a second lithium salt at a second molar concentration lower than the first molar concentration.

[0015] The battery cell may include a passivation film formed at the interface between the electrode tab and the gel electrolyte by combining a first lithium salt with a cation of the electrode tab. The passivation film may include at least one of AlF3 and LiF.

[0016] Meanwhile, the first lithium salt and the second lithium salt may be the same or different. The first lithium salt may include at least one of LiPF6 (Lithium hexafluorophosphate) and LiBF4 (Lithium tetrafluoroborate), and the second lithium salt may include at least one of LiPF6, LiFSI (Lithium bis(fluorosulfonyl)imide), LiTFSI (Lithium bis(trifluoromethanesulfonyl)imide), and LiBOB (Lithium bis(oxalato)borate).

[0017] On the other hand, the second molar concentration of the second lithium salt may be lower than the first molar concentration of the first lithium salt by 0.1 M or more, and specifically, the ratio of the second molar concentration of the second lithium salt to the first molar concentration of the first lithium salt may be 1:1.3 to 1:5.

[0018] Meanwhile, the gel electrolyte may be located only on one side of the electrode assembly where the electrode tabs are formed in the receiving space in order to prevent the electrode tabs inside the battery cell from moving or deforming due to an external impact, and the liquid electrolyte may be configured to surround the other side of the electrode assembly where the gel electrolyte is not formed.

[0019] According to another embodiment, the present invention provides a battery module including at least one battery cell of the present invention.

[0020] According to another embodiment, the present invention provides a method for manufacturing a battery, the method comprising the steps of: preparing an electrode assembly including a plurality of electrodes, electrode tabs formed on at least one side of each of the plurality of electrodes, and separators interposed between the plurality of electrodes; placing the electrode assembly in an accommodating space of a cell case; a gel electrolyte composition including a first lithium salt having a first molar concentration and a curable compound is injected into the receiving space, and then the gel electrolyte composition is disposed around the electrode tab; curing the gel electrolyte composition to form a gel electrolyte surrounding the electrode tabs; and injecting a liquid electrolyte containing a second lithium salt at a second molar concentration so as to be contained between the plurality of electrodes.

[0021] Meanwhile, the method may further include forming a barrier between the receiving space of the cell case and the injection space for the gel electrolyte composition before injecting the gel electrolyte composition. [Effects of the Invention]

[0022] In the battery cell according to the present invention, a gel electrolyte with low fluidity is disposed around the electrode tabs, and when an external impact is applied to the battery cell, the semi-solid gel electrolyte formed around the electrode tabs minimizes the movement and deformation of the electrode tabs. As a result, when the battery cell according to the present invention is installed in a vehicle, even if the battery cell is subjected to continuous impacts and vibrations that occur during travel, damage to the electrode tabs can be minimized and breakage of the electrode tabs can be prevented, thereby effectively improving the performance and lifespan of the battery cell.

[0023] In addition, the battery cell according to the present invention uses a liquid electrolyte in addition to a gel electrolyte, thereby improving wettability to the electrode assembly and effectively reducing manufacturing time and costs.

[0024] Furthermore, the battery cell according to the present invention allows the first lithium salt in the gel electrolyte to migrate to the liquid electrolyte due to a molar concentration gradient between the first lithium salt in the gel electrolyte and the second lithium salt in the liquid electrolyte, and replenishes the lithium salt in the liquid electrolyte that is lost due to lithium precipitation or the like during charge and discharge, thereby providing a lithium secondary battery and battery module with effectively improved cycle characteristics. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a plan view showing a battery cell according to an embodiment of the present invention. [Figure 2] 1 is an exploded perspective view showing a pouch and an electrode assembly of a battery cell according to an embodiment of the present invention; [Figure 3] FIG. 2 is an exploded perspective view showing a separator and an electrode according to an embodiment of the present invention. [Figure 4] FIG. 2 is a vertical cross-sectional view showing the interior of a battery cell according to one embodiment of the present invention. [Figure 5] FIG. 2 is a plan view showing the interior of a battery cell according to an embodiment of the present invention. [Figure 6]10 is a front view showing a state in which a plurality of electrodes are inserted into the storage space of the pouch in a method for manufacturing a battery cell according to one embodiment of the present invention. FIG. [Figure 7] FIG. 2 is a front view showing the interior of a pouch in which a gel electrolyte composition is being injected into the storage space in a battery cell manufacturing method according to one embodiment of the present invention. [Figure 8] FIG. 2 is a front view showing the state inside the pouch where the gel electrolyte composition is thermally cured in the storage space in the battery cell manufacturing method according to one embodiment of the present invention. [Figure 9] FIG. 2 is a side view showing a state before the battery cell is fixed using a fixing jig while the gel electrolyte composition is hardening, in a battery cell manufacturing method according to one embodiment of the present invention. [Figure 10] FIG. 10 is a side view showing a state in which a battery cell is fixed using a fixing jig while a gel electrolyte composition is hardening in a battery cell manufacturing method according to one embodiment of the present invention. [Figure 11] FIG. 10 is a perspective view showing the interior of a pouch in which a liquid electrolyte is being poured into the storage space in a method for manufacturing a battery cell according to one embodiment of the present invention. [Figure 12] 10 is a front view showing a state in which one side of the pouch containing space is further sealed in a method for manufacturing a battery cell according to one embodiment of the present invention. FIG. [Figure 13] FIG. 10 is a front view showing the state in which the injection space of the pouch has been removed in the battery cell manufacturing method according to one embodiment of the present invention. [Figure 14] 1 is a perspective view schematically illustrating a battery module according to an embodiment of the present invention. [Figure 15] 5 is a partially enlarged view schematically showing an enlarged view of region A of the battery cell in FIG. 4. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention will be described in detail below with reference to the drawings. When describing the present invention, detailed descriptions of related well-known functions or configurations will be omitted if it is determined that such descriptions may unnecessarily obscure the gist of the present invention. It should be noted that the following embodiments may be modified into various different forms, and the scope of the technical concept of the present invention is not limited to the following embodiments. These embodiments are provided to make the present invention more complete and complete, and to fully convey the technical concept of the present invention to those skilled in the art.

[0027] It should be understood that the technology described in the present invention is not limited to the particular embodiments, but includes various modifications, equivalents, and / or alternatives of the embodiments of the present invention.

[0028] In connection with the description of the drawings, like reference numerals may be used for like components. In the present invention, the terms "have," "can have," "include," or "can include" refer to the presence of a given feature (e.g., a value, a function, an operation, or a component such as a part) and do not exclude the presence of additional features.

[0029] In the present invention, expressions such as "A or B," "at least one of A and / or B," or "one or more of A and / or B" can include all possible combinations of the items listed together. For example, "A or B," "at least one of A and B," or "at least one of A or B" can refer to (1) at least one A, (2) at least one B, or (3) both at least one A and at least one B.

[0030] The inventors conducted extensive research to develop a battery cell with excellent performance and lifespan that prevents breakage due to the flow and deformation of the electrode tabs and has discovered that disposing a gel electrolyte with low fluidity around the electrode tabs so as to surround them and disposing a liquid electrolyte with excellent wettability around the electrode assembly where no gel electrolyte is present can significantly prevent breakage of the electrode tabs and improve cycle characteristics, leading to the completion of the present invention. Furthermore, the inventors discovered that the lifespan and performance of a battery can be effectively improved by injecting a liquid electrolyte with a low lithium salt concentration and low viscosity to improve the impregnation of the electrode assembly with the electrolyte, and by using a gel electrolyte with a relatively high molar concentration of lithium salt in combination to replenish the lithium salt in the liquid electrolyte that is lost during charge and discharge, leading to the completion of the present invention.

[0031] Specifically, the battery cell 100 according to the present invention includes a cell case 110 , an electrode assembly 120 , electrode tabs 121 , a gel electrolyte 150 surrounding the periphery of the electrode tabs, and a liquid electrolyte 160 . The configuration of the battery cell of the present invention will be specifically described below.

[0032] Battery cell FIG. 1 shows a plan view of a battery cell 100 according to one embodiment of the present invention. FIG. 2 shows an exploded perspective view of a pouch and electrode assembly 120 of the battery cell 100 according to one embodiment of the present invention. FIG. 3 shows an exploded perspective view of a separator 170 and electrodes 122p, 122n according to one embodiment of the present invention. FIG. 4 shows a vertical cross-sectional view showing the interior of the battery cell 100 according to one embodiment of the present invention. FIG. 5 shows a plan view showing the interior of the battery cell 100 according to one embodiment of the present invention. For reference, for ease of explanation, the gel electrolyte 150 and the liquid electrolyte 160 are omitted in FIG. 2, and the first cell sheet 114T of the battery cell 100 is removed in FIG. 5.

[0033] First, referring to Figures 1 and 2, a battery cell 100 of the present invention includes a cell case 110, a seal portion 111 heat-sealed to the outer periphery, and an electrode lead portion 130 including a positive electrode lead 130a and a negative electrode lead 130b protruding to the outside of the cell case, and a portion of the cell case may have a portion (P) protruding outward in a convex shape so as to accommodate an electrode assembly (not shown).

[0034] The cell case 110 may be a pouch-type case made of a flexible material. Specifically, as shown in FIG. 2, the cell case 110 may include a first cell sheet 114T covering the upper portion of the electrode assembly 120 and a second cell sheet 114P coupled to a portion of the lower surface of the first cell sheet 114T and covering the lower portion of the electrode assembly 120. In this case, each of the first cell sheet 114T and the second cell sheet 114P may be a laminate sheet. Specifically, the laminate sheet may have a structure in which a thin metal film (e.g., an Al film) is laminated between a water-resistant polymer film (e.g., nylon) and a heat-adhesive polymer film (e.g., cast polypropylene). The structure of the laminate sheet and the materials constituting each layer are well known in the art, and therefore will not be described in detail.

[0035] The cell casing 110 can be sealed by heat-sealing portions of the first cell sheet 114T and the second cell sheet 114P to each other. The heat-sealing method can include pressing at least a portion of the opposing outer peripheries of the first cell sheet 114T and the second cell sheet 114P in a stacked state using a high-temperature tool (e.g., a hot press). At this time, the heat-sealing temperature can be 110°C to 150°C. As a result of this heat-sealing, a heat-sealed seal portion 111 can be formed on the outer periphery of the cell casing 110, as shown in FIG. 1.

[0036] 2 to 5, the cell casing 110 may include a receiving space 110p1 that receives the electrode assembly 120, the electrode tabs 121, the gel electrolyte 150, and the liquid electrolyte 160. The receiving space 110p1 may be a cup-shaped portion formed by pressing a portion of at least one of the two cell sheets 114T and 114P using a high-temperature hot press. The receiving space 110p1 may be a portion (P) of each of the cell sheets 114T and 114P that protrudes outward. The receiving space 110p1 of the cell casing 110 may be large enough to receive all of the electrodes 122, the separator 170, the gel electrolyte 150, and the liquid electrolyte 160. For example, as shown in FIG. 2, the storage space 110p1 of the cell case 110 can be formed by combining a portion (P) of the first cell sheet 114T that protrudes convexly upward and a portion (R) of the second cell sheet 114P that is recessed downward.

[0037] Meanwhile, the electrode assembly 120 is an electrode assembly having a structure in which a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode are sequentially stacked. FIG. 2 shows a structure in which the pouch and electrode assembly 120 of the battery cell 100 according to the present invention are separated, and FIG. 3 shows a structure in which the separator 170 and electrodes 122, i.e., the positive electrode 122p and the negative electrode 122n, of the electrode assembly 120 according to the present invention are separated.

[0038] As shown in FIG. 3, the electrodes 122 can include at least one positive electrode 122p and at least one negative electrode 122n depending on the electrical polarity. The positive electrode 122p has a structure in which a positive electrode active material layer is formed on a current collector (not shown). In this case, the positive electrode active material layer may include a positive electrode active material, and optionally a conductive material and a binder. For example, the positive electrode 122p may be formed by applying a mixture of the positive electrode active material, the conductive material, and the binder to a current collector made of aluminum alloy foil.

[0039] The negative electrode 122n has a structure in which a negative electrode active material layer is formed on a current collector (not shown). In this case, the negative electrode active material layer may include a negative electrode active material, and optionally a conductive material and a binder. For example, the negative electrode 122n may be formed by applying a mixture of a negative electrode active material, a conductive material, and a binder to a current collector made of a copper alloy foil.

[0040] The positive electrode active material, negative electrode active material, binder, and conductive material may be any known material used in lithium secondary batteries. A separator 170 may be interposed between the positive electrode 122p and the negative electrode 122n. The separator 170 may serve to prevent an internal short circuit between the positive electrode 122p and the negative electrode 122n and to allow the electrolyte to be impregnated therebetween. The separator 170 of the present invention may be made of any separator material commonly used in secondary batteries. For example, the separator 170 may be made of at least one of polyethylene and polypropylene. The positive electrode 122p, the separator 170, and the negative electrode 122n may be stacked in this order to form an electrode assembly 120 as shown in FIG. 2.

[0041] Meanwhile, an electrode tab 121 may be attached to the electrode current collector as a path through which electrons can move. The electrode tab 121 may not be coated with the mixture of the electrode active material, conductive material, and binder. That is, the electrode tab 121 may be formed by cutting an uncoated portion of an electrode collector that is not coated with an electrode active material, or may be formed separately by connecting a separate conductive member to the uncoated portion of the electrode collector by ultrasonic welding or the like.

[0042] At least one electrode tab 121 may be provided for each of the positive and negative electrodes. For example, as shown in FIG. 3, a positive electrode tab 121a and a negative electrode tab 121b protruding from a first side 122n1 may be provided on the positive electrode 122p and the negative electrode 122n, respectively. However, this is not necessarily limited to this configuration. For example, the positive electrode tab 121a and the negative electrode tab 121b may be formed on at least one of a first side 122p1, a second side 122p2, a third side 122p3, and a fourth side 122p4 in the front-rear and left-right directions of the electrode 122. For example, if the positive electrode 122p has a rectangular shape in plan view, the positive electrode tab 121a may be formed on at least one of a first side 122p1, a second side 122p2, a third side 122p3, and a fourth side 122p4. When the negative electrode 122n has a rectangular shape in plan view, the negative electrode tab 121b may be formed on at least one of the first side 122n1, the second side 122n2, the third side 122n3, and the fourth side 122n4.

[0043] Meanwhile, as shown in FIG. 2, the battery cell 100 according to an embodiment of the present invention may further include an electrode lead 130 coupled to a portion of the electrode tab 121. The electrode lead 130 may be made of a conductive metal. Referring to FIG. 2, the electrode lead 130 may include a positive electrode lead 130a coupled to the positive electrode tab 121a and a negative electrode lead 130b coupled to the negative electrode tab 121b. The electrode lead 130 may be coupled to one or more electrode tabs 121 by various methods, such as welding. A portion of the electrode lead 130 may be exposed to the outside of the cell casing 110. That is, the electrode lead 130 serves as an electrode terminal of the battery cell 100. For example, the positive electrode lead 130a may serve as the positive electrode terminal of the battery cell 100, and the negative electrode lead 130b may serve as the negative electrode terminal of the battery cell 100. The battery cell 100 may include an insulating film 140 configured to surround a portion of the outer surface of the electrode lead 130. The insulating film 140 provides electrical insulation between the cell casing 110 and the electrode lead 130, and may be configured to be heat-sealed to the cell casing 110.

[0044] Meanwhile, referring to FIGS. 4 and 5, in the battery cell of the present invention, a gel electrolyte 150 with low fluidity may be disposed around the electrode tabs 121, including the positive electrode tab 121a and the negative electrode tab 121b, so as to surround the electrode tabs 121.

[0045] The gel electrolyte 150 refers to an electrolyte having a gel phase. Here, the gel phase can be phenomenologically defined as a soft, semi-solid substance containing at least one liquid, and due to its high viscosity, it does not flow in a steady state and maintains a certain shape.

[0046] The gel electrolyte 150 may include a curable compound that can be cured to such an extent that the electrolyte exhibits a gel phase, and may further include an organic solvent and a first lithium salt.

[0047] The gel electrolyte 150 is mostly liquid by weight and may contain some solid material. For example, the gel electrolyte 150 may be manufactured by thermally curing or UV curing a curable compound mixed with a liquid electrolyte to change the phase into a gel electrolyte.

[0048] The gel electrolyte 150 may be located on one side of the electrode assembly 120 where the electrode tab 121 is located in the receiving space 110p1 so as to prevent the electrode tab 121 from moving due to an external impact on the battery cell 100. That is, the gel electrolyte 150 may surround the outer surface of the electrode tab 121 so as to prevent the electrode tab 121 from moving and deforming.

[0049] For example, as shown in FIG. 4, the gel electrolyte 150 may be located between the inner surface of the receiving space 110p1 and the first side 120a of the electrode assembly 120 where the electrode tab 121 is located. In this case, the gel electrolyte 150 may surround the outer surfaces of the positive electrode tab 121a and the negative electrode tab 121b to prevent the positive electrode tab 121a and the negative electrode tab 121b from moving, respectively. However, this is not necessarily limited to this configuration. For example, if the electrode tab 121 is located on at least one of the first side 120a, the second side 120b, the third side 120c, and the fourth side 120d of the electrode assembly 120, the gel electrolyte 150 may be located on at least one of the first side 120a, the second side 120b, the third side 120c, and the fourth side 120d of the electrode assembly 120 where the electrode tab 121 is located. Additionally, the gel electrolyte 150 can be configured to surround the outer surface of the electrode tab 121. In particular, the gel electrolyte 150 can be configured to surround the interface between the electrode tab 121 and the electrode lead 130.

[0050] Meanwhile, the gel electrolyte 150 does not necessarily have to be located only on one side where the electrode tabs 121 are formed, but the gel electrolyte 150 may also be located on other sides of the electrode assembly 120 where the electrode tabs 121 are not located. For example, in the case of Fig. 5, the gel electrolyte 150 may be located in a portion of the space between the electrode assembly 120 and the cell casing 110 on each of the second side 120b and the fourth side 120d of the electrode assembly 120 where the electrode tabs 121 are not located.

[0051] According to this configuration of the present invention, in the battery cell 100, the gel electrolyte 150 surrounds the electrode tab 121, compared to the conventional battery cell 100 in which the liquid electrolyte 160 surrounds the electrode tab 121. Therefore, when an external impact is applied to the battery cell 100, the gel electrolyte 150 prevents the electrode tab 121 from moving, thereby preventing the connection portion between the electrode tab 121 and the electrode 122 or the bent portion of the electrode tab 121 from being broken due to frequent movement of the electrode tab 121.

[0052] That is, when the battery cell 100 of the present invention is mounted in an automobile, even if the battery cell 100 is subjected to frequent shocks and vibrations that occur during travel, the semi-solid gel electrolyte 150 minimizes the flow and deformation of the electrode tabs 121, thereby preventing breakage of the electrode tabs 121. This prevents inactivation of the electrodes 122 during charging and discharging, thereby effectively extending the life of the battery cell 100.

[0053] As shown in FIG. 4, the battery cell 100 of the present invention can also include a liquid electrolyte 160. The liquid electrolyte 160 may be accommodated adjacent to the inside of the cell case 110 so as to be in contact with the gel electrolyte 150. In this case, an interface (X) may be formed between the gel electrolyte 150 and the liquid electrolyte 160. The battery cell 100 of the present invention may be configured so that the first lithium salt of the gel electrolyte 150 can migrate to the liquid electrolyte 160 through the interface (X) between the gel electrolyte 150 and the liquid electrolyte 160. That is, the battery cell 100 of the present invention is configured so that the first lithium salt of the gel electrolyte 150, which has a relatively high concentration, can migrate to the liquid electrolyte 160 through the interface (X) between the gel electrolyte 150 and the liquid electrolyte 160. Therefore, even if the battery cell 100 is charged and discharged multiple times, depletion of the lithium salt in the liquid electrolyte 160, which has a relatively low molar concentration, can be prevented, thereby effectively increasing the lifespan of the battery cell 100.

[0054] 4 and 5, the liquid electrolyte 160 may be accommodated in the accommodation space 110p1 to surround at least one other side of the electrode assembly 120 where the gel electrolyte 150 is not formed, for example, where the electrode tab 121 is not located. When the electrode tab 121 is located on the first side 120a of the electrode assembly 120, the liquid electrolyte 160 may be located on one of the remaining second side 120b, third side 120c, and fourth side 120d of the electrode assembly 120 where the electrode tab 121 is not formed. It is preferable to position the liquid electrolyte 160 on the side with as much liquid electrolyte 160 as possible so that a large amount of liquid electrolyte 160 can be replenished in preparation for consumption of the liquid electrolyte 160, thereby effectively preventing a decrease in the lifespan of the battery cell 100. For example, as shown in FIG. 5, when the electrode tab 121 is located on the first side 120a of the electrode assembly 120, the liquid electrolyte 160 can be located to surround the remaining second side 120b, third side 120c, and fourth side 120d of the electrode assembly 120.

[0055] According to this configuration of the present invention, when the liquid electrolyte 160 located between the electrodes 122 is consumed during charging and discharging of the battery cell 100, the liquid electrolyte 160 located on the other side of at least one of the electrodes 122 where the electrode tabs 121 are not formed can move between the electrodes 122 to replenish the liquid electrolyte 160. Therefore, even if the liquid electrolyte 160 between the electrodes 122 is consumed after multiple charging and discharging of the battery cell 100, the reduction in the lifespan of the battery cell 100 can be suppressed.

[0056] 15, an insoluble passivation film 123 may be formed on the metal surface of the electrode tab 121 through a reaction between anions of the lithium salt contained in the gel electrolyte 150 and cations of the electrode tab 121. The passivation film 123 prevents corrosion by suppressing a reduction reaction on the surface of the electrode tab, minimizes damage to the electrode tab 121 due to external impact, and effectively prevents breakage of the electrode tab 121.

[0057] Furthermore, the battery cell 100 according to one embodiment of the present invention can be charged and discharged by ion exchange between the positive electrode 122p and the negative electrode 122n via the liquid electrolyte 160. The liquid electrolyte 160 can be located between the positive electrode 122p and the negative electrode 122n to allow ions to move between the positive electrode 122p and the negative electrode 122n. The liquid electrolyte 160 can be absorbed into each of the positive electrode 122p and the negative electrode 122n. The liquid electrolyte 160 can be located on the surface and in the pores of the separator 170. For example, in the case of a lithium secondary battery, the battery cell 100 can typically use a nonaqueous electrolyte. Next, each component of the gel electrolyte 150 and liquid electrolyte 160 contained in the battery cell of the present invention will be described in more detail.

[0058] (1) Gel electrolyte The gel electrolyte 150 of the present invention can be formed by injecting a gel electrolyte composition 155 containing a curable compound, a first lithium salt, an organic solvent, and a polymerization initiator into the accommodation space 110p1 and then performing thermal polymerization.

[0059] In this case, the curable compound is not particularly limited as long as it has a polymerizable functional group selected from the group consisting of a vinyl group, an epoxy group, an allyl group, and a (meth)acrylic group, in which a polymerization reaction can occur within the structure, forms a crosslinked bond by a polymerization reaction that is commonly used in the production of gel electrolytes, and can be converted into a gel phase.

[0060] Specifically, the curable compound may be at least one selected from a polymerizable monomer, an oligomer, and a copolymer. The polymerizable monomer may include a thermally polymerizable monomer or an ultraviolet-curable acrylate monomer.

[0061] Representative examples of the thermally polymerizable monomer include tetraethylene glycol diacrylate, polyethylene glycol diacrylate (molecular weight 50 to 20,000), 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, and pentaerythritol ethoxylate tetraacrylate. tetraacrylate), dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, poly(ethylene glycol) diglycidylether, 1,5-hexadiene diepoxide, glycerol propoxylate triglycidyl ether, vinylcyclohexene dioxide, 1,2,7,8-diepoxyoctane (1,2,7,The monomer may be at least one of 8-diepoxyoctane, 4-vinylcyclohexene dioxide, butyl glycidyl ether, diglycidyl 1,2-cyclohexanedicarboxylate, ethylene glycol diglycidyl ether, glycerol triglycidyl ether, and glycidyl methacrylate, and these monomers may be used alone or in combination of two or more.

[0062] In addition, the UV-curable acrylate monomer may include at least one of octyl / decyl acrylate (ODA), isodecyl acrylate (IDA), lauryl acrylate (LA), stearyl acrylate (SA), phenoxyethyl acrylate (PEA), nonylphenol ethoxylate monoacrylate (MNPEOA), tetrahydrofurfuryl acrylate, cyclohexyl acrylate, 4-butylcyclohexyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, 4-hydroxybutyl acrylate (4-HBA), and phenoxyethyl acrylate. The oligomer may include at least one selected from the group consisting of a fluorine-based oligomer, a polyether-based oligomer, a polycarbonate-based oligomer, an acrylate-based oligomer, a polysiloxane-based oligomer, a phosphazene-based oligomer, a polyethylene-based oligomer, a urethane-based oligomer, an epoxy-based oligomer, polyethylene oxide, polyester sulfide, polyvinyl alcohol, and polyvinylidene fluoride, and more specifically, may include at least one selected from a fluorine-based oligomer, a polycarbonate-based oligomer, and a polysiloxane-based oligomer. The copolymer can include at least one selected from the group consisting of allyl 1,1,2,2-tetrafluoroethyl ether (TFE)-(2,2,2-trifluoroethyl acrylate) copolymer, TFE-vinyl acetate copolymer, TFE-(2-vinyl-1,3-dioxolane) copolymer, TFE-vinyl methacrylate copolymer, TFE-methyl acrylate copolymer, TFE-methyl methacrylate (MMA) copolymer, and TFE-2,2,2-trifluoroethyl acrylate copolymer.

[0063] The curable compound may be contained in an amount of about 3 wt% to 30 wt%, preferably about 3 wt% to 25 wt%, more preferably about 3 wt% to 10 wt%, specifically 5 wt% to 7 wt%, based on the total weight of the gel electrolyte composition.

[0064] If the content of the curable compound is less than 3 wt % relative to the total weight of the gel electrolyte composition 155, the electrolyte is unlikely to form a gel phase even when the curable compound cures. Furthermore, if the content of the curable compound exceeds 30 wt % relative to the total weight of the gel electrolyte composition 155, the viscosity of the gel electrolyte composition 155 increases. This reduces the fluidity of the gel electrolyte composition 155 when injected into the storage space of the battery cell 100. This makes it difficult to move the gel electrolyte composition 155 to the storage space 110p1 around the electrode tab 121. Part of the gel electrolyte composition 155 may remain between the electrodes 122 during the movement. The gel electrolyte composition 155 remaining between the electrodes 122 has a higher ion conduction resistance than the liquid electrolyte 160, which may adversely affect the performance of the battery cell 100 (e.g., increase the internal resistance of the battery). Therefore, if the content of the curable compound in the gel electrolyte composition 155 satisfies the above range, the gel electrolyte composition can have a viscosity that facilitates injection into the storage space.

[0065] Meanwhile, the first lithium salt is not particularly limited as long as it contains an anion that can form an insoluble passivation film on the metal surface of the electrode tab and can suppress the induction of a reduction reaction on the surface of the electrode tab. Specifically, examples of the first lithium salt include LiPF, LiCl, LiBr, LiI, LiBF, LiClO, and LiB. 10 Cl 10 , LiAlCl4, LiAlO4, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, and LiCH3SO3, and preferably, any one of LiPF6 and LiBF4.

[0066] Specifically, when the first lithium salt is one of LiPF6 and LiBF4, the first anion is F - and the first anion (F - ) and the cation (Al 3+15, an aluminum native oxide (Al2O3) film 124 is formed on the surface of the electrode tab 121 containing aluminum, and a passivation film 123 may be formed on the aluminum native oxide film. The passivation film 123 may include at least one of AlF3 and LiF.

[0067] On the other hand, when LiFSI (Lithium bis(fluorosulfonyl)imide) or LiTFSI (Lithium bis(trifluoromethanesulfonyl)imide) is used as the first lithium salt, it reacts with the aluminum metal surface of the electrode tab to generate Al(FSI)3 (Al((FSO2)2N)3) on the surface of the electrode tab. This reaction product is soluble in the electrolyte solvent and may dissolve in the electrolyte solvent, causing corrosion of the electrode tab. Therefore, the present invention uses LiPF6 and LiBF4 or the like as the first lithium salt to generate AlF3, LiF, or the like that has low solubility (or is insoluble) in the electrolyte solvent before Al(FSI)3, and forms a passivation film 123 on the aluminum metal surface of the electrode tab, thereby suppressing the corrosion reaction of the aluminum metal of the electrode tab.

[0068] However, LiPF6 and LiBF4 have the disadvantage of lower ionic conductivity and thermal stability compared to LiFSI (Lithium bis(fluorosulfonyl)imide), LiTFSI (Lithium bis(trifluoromethanesulfonyl)imide), or LiBOB (Lithium bis(oxalato)borate). However, as will be described later, the battery cell 100 of the present invention can improve the disadvantages of LiPF6, LiBF4, and the like, such as low ionic conductivity and thermal stability, by using a liquid electrolyte 160 with high ionic conductivity and thermal stability in combination.

[0069] Meanwhile, the first molar concentration of the first lithium salt may be 0.6M to 5.0M. Here, the first molarity refers to the amount of solute dissolved in 1 liter of solution, expressed in moles. When the molarity of the first lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, thereby exhibiting excellent electrolyte performance and allowing lithium ions to migrate effectively.

[0070] On the other hand, if the first molar concentration of the first lithium salt in the gel electrolyte 150 is less than 0.2 M, the excessively low concentration of the first lithium salt will not effectively increase the lifespan of the battery cell 100. Also, if the first molar concentration of the first lithium salt in the gel electrolyte 150 exceeds 5.0 M, the use of an excessive amount of lithium salt will increase the viscosity of the gel electrolyte composition, thereby reducing the fluidity of the gel electrolyte composition. As a result, the gel electrolyte will not fill the entire space around the electrode tab, and the liquid electrolyte will penetrate, which may cause breakage of the tab and a decrease in lifespan. Specifically, the first molar concentration of the first lithium salt may be 0.9M to 4.0M, specifically 1.0M to 3.0M.

[0071] The organic solvent is not particularly limited as long as it is an organic solvent used in secondary battery electrolytes. Specifically, it may be one or more selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), vinylene carbonate (VC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), and γ-butyrolactone. However, the organic solvent is not necessarily limited to the above-listed structures, and similar effects can be achieved by using known structures and their equivalents. Meanwhile, the remainder of the gel electrolyte composition of the present invention, excluding the curable compound, lithium salt, and polymerization initiator, may be an organic solvent unless otherwise specified.

[0072] As the polymerization initiator, a conventional thermal polymerization initiator or photopolymerization initiator well known in the art can be used depending on the type of curable compound. Specifically, when a thermally polymerizable monomer is used as the curable compound, a thermal polymerization initiator can be used as the polymerization initiator, and when an ultraviolet-curable acrylate monomer is used as the curable compound, a photopolymerization initiator can be used as the polymerization initiator.

[0073] The thermal polymerization initiator is decomposed by heat to form radicals, which react with the polymerizable monomer, oligomer, or copolymer through free radical polymerization to gel the gel electrolyte composition. Specific non-limiting examples of the thermal polymerization initiator include benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butyl peroxide, t-butyl peroxy-2-ethylhexanoate, cumyl hydroperoxide, and hydrogen peroxide. peroxide), and azo compounds such as 2,2'-azobis(2-cyanobutane), 2,2'-azobis(methylbutyronitrile), 2,2'-azobis(isobutyronitrile) (AIBN), and 2,2'-azobisdimethylvaleronitrile (AMVN).

[0074] The thermal polymerization initiator is decomposed by heat, for example, at 30°C to 100°C, or at room temperature (5°C to 30°C) in the battery to form radicals, and the polymerizable monomer reacts with the acrylate compound through free radical polymerization to form the gel electrolyte 150.

[0075] The photopolymerization initiator can be decomposed by light to form radicals, which can react with the polymerizable monomer, oligomer, or copolymer through free radical polymerization to gel the gel electrolyte composition.Specifically, non-limiting examples of the photopolymerization initiator can include at least one of ethyl benzoin ether, isopropyl benzoin ether, α-methylbenzoin ethyl ether, benzoin phenyl ether, α-acyloxime ester, 1,1-dichloroacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, anthraquinone, 2-anthraquinone, 2-chloroanthraquinone, thioxanthone, isopropylthioxanthone, chlorothioxanthone, benzophenone, benzyl benzoate, and benzoyl benzoate.

[0076] The polymerization initiator may be included in an amount of 0.01 to 20 parts by weight, specifically 0.1 to 10 parts by weight, based on 100 parts by weight of the curable compound. When the polymerization initiator is included in an amount within the range of 0.01 to 20 parts by weight, the conversion rate of the curable compound can be increased, thereby ensuring the properties of the gel electrolyte 150.

[0077] On the other hand, the gel electrolyte composition before forming the gel electrolyte 150 preferably has a viscosity of about 3 cP to 100 cP, specifically 6 cP to 10 cP, and more specifically 6 cP to 7 cP, so as to be easily poured into the containing space 110p1.

[0078] If the viscosity of the gel electrolyte composition 155 is less than 3 cP, the electrode tabs 121 may flow, resulting in disconnection of the electrode tabs 121. Conversely, if the viscosity of the gel electrolyte composition 155 is more than 100 cP, the fluidity of the gel electrolyte composition 155 may decrease, making it difficult to move the gel electrolyte composition into the storage space around the electrode tabs. In addition, the increased amounts of the curable compound and first lithium salt contained therein may increase the manufacturing cost of the battery cell 100.

[0079] Furthermore, the viscosity of the hardened gel electrolyte after the formation of the gel electrolyte 150 is about 10,000 cP to 30,000 cP, specifically 20,000 cP, and the gel electrolyte may have a viscosity with almost no fluidity.

[0080] In the present invention, when the viscosity of the gel electrolyte 150 satisfies the above range, even if frequent impacts and vibrations that occur during transportation are transmitted to the battery cell 100, the electrolyte 150, which has a higher viscosity than the liquid electrolyte 160, can minimize the flow and deformation of the electrode tab 121.

[0081] As described above, the present invention controls the viscosity of the gel electrolyte 150 to have a suitable viscosity that can prevent the flow and deformation of the electrode tabs 121 by adjusting the content of the first lithium salt having a first molar concentration and the hardened polymer. This can reduce deformation of the electrode tabs 121 even when an external impact is applied to the battery cell 100. Therefore, when the battery cell 100 of the present invention is installed in a vehicle, even if the battery cell 100 is subjected to frequent impacts and vibrations that occur during travel, the electrolyte 150, which has a higher viscosity than the liquid electrolyte 160, can minimize the flow and deformation of the electrode tabs 121.

[0082] (2)Liquid electrolyte In the present invention, the liquid electrolyte comprises a second lithium salt and an organic solvent, and may optionally further comprise an additive.

[0083] The molar concentration of the second lithium salt in the liquid electrolyte may be about 0.5M to 2.0M. On the other hand, if the second molar concentration of the second lithium salt in the liquid electrolyte 160 is less than 0.5 M, the lithium ion conductivity decreases, the internal resistance of the battery cell increases, and the life of the battery cell 100 may be shortened. Also, if the second molar concentration of the second lithium salt exceeds 2.0 M, the amount of the second lithium salt used increases more than necessary, the viscosity of the liquid electrolyte 160 increases, and the wettability of the liquid electrolyte 160 to the electrode assembly 120 may decrease, resulting in an increase in the manufacturing cost of the battery cell. The molar concentration of the second lithium salt in the liquid electrolyte may be about 0.75M to 1.8M, specifically about 0.8M to 1.5M.

[0084] In particular, in the present invention, the liquid electrolyte preferably contains a second lithium salt at a second molar concentration lower than the first molar concentration of the first lithium salt in the gel electrolyte so as to form a concentration gradient. Specifically, the second molar concentration of the second lithium salt is preferably at least 0.1 M lower than the first molar concentration of the first lithium salt.

[0085] In the present invention, by setting the second molar concentration of the second lithium salt in the liquid electrolyte 160 to be 0.1 M or more lower than the first molar concentration of the first lithium salt in the gel electrolyte 150, a suitable concentration gradient of the lithium salts in the gel electrolyte 150 and the liquid electrolyte 160 can be formed, and the first lithium salt in the gel electrolyte 150 can migrate to the liquid electrolyte 160 through the interface (X) between the gel electrolyte 150 and the liquid electrolyte 160. On the other hand, when the second molar concentration of the second lithium salt in the liquid electrolyte 160 is set to be 0.1 M or more lower than the first molar concentration of the first lithium salt in the gel electrolyte 150, is In this case, the amount of the first lithium salt in the gel electrolyte 150 that migrates to the liquid electrolyte 160 is small, and the effect of improving the life of the battery cell 100 may be insignificant.

[0086] Specifically, in the battery cell 100 according to one embodiment of the present invention, the first molar concentration of the first lithium salt in the gel electrolyte 150 is 0.6 M to 5.0 M, and the second molar concentration of the second lithium salt in the liquid electrolyte 160 is 0.5 M to 2.0 M. In this case, the second molar concentration of the second lithium salt may be lower than the first molar concentration of the first lithium salt by 0.1 M or more. Preferably, the second molar concentration of the second lithium salt in the liquid electrolyte 160 may be 0.75 M to 1.8 M, and more preferably 0.8 M to 1.5 M. In this manner, by setting the second molar concentration of the second lithium salt to be lower than the first molar concentration of the first lithium salt by 0.1 M or more, an appropriate concentration gradient of the lithium salts in the gel electrolyte 150 and the liquid electrolyte 160 can be formed, thereby allowing the first lithium salt in the gel electrolyte 150 to migrate to the liquid electrolyte 160.

[0087] In addition, in the battery cell 100 according to one embodiment of the present invention, the ratio of the second molar concentration of the second lithium salt to the molar concentration of the first lithium salt may be 1:1.3 to 1:5. Preferably, the ratio of the second molar concentration of the second lithium salt to the molar concentration of the first lithium salt may be 1:1.3 to 1:5. More preferably, the ratio of the second molar concentration of the second lithium salt to the molar concentration of the first lithium salt may be 1:1.4 to 1:5.

[0088] In the present invention, when the ratio of the second molar concentration of the second lithium salt to the molar concentration of the first lithium salt is within the above range, an appropriate concentration gradient of the lithium salts in the gel electrolyte 150 and the liquid electrolyte 160 can be formed, and the first lithium salt in the gel electrolyte 150 can migrate to the liquid electrolyte 160 via the interface (X).

[0089] On the other hand, if the ratio of the second molar concentration of the second lithium salt to the molar concentration of the first lithium salt is less than 1:1.3, it is difficult to obtain an appropriate concentration gradient, and the amount of the first lithium salt in the gel electrolyte 150 that migrates to the liquid electrolyte 160 is small, which may result in a negligible effect on extending the life of the battery cell 100. Also, if the ratio of the second molar concentration of the second lithium salt to the molar concentration of the first lithium salt is greater than 1:5, the amount of the first lithium salt used in the gel electrolyte 150 increases unnecessarily, which may make it difficult to inject the gel electrolyte composition and may increase the manufacturing cost of the battery cell 100.

[0090] On the other hand, typical examples of second lithium salts include LiPF6, LiCl, LiBr, LiI, LiBF4, LiClO4, and LiB 10 Cl 10The second lithium salt may include a single substance or a mixture of two or more substances selected from the group consisting of LiAlCl, LiAlO, LiCFSO, LiCHCO, LiCFCO, LiAsF, LiSbF, LiCHSO, LiFSI (Lithium bis(fluorosulfonyl)imide, LiN(SOF)), LiTFSI (Lithium(bis)trifluoromethanesulfonimide, LiN(SOCF)), LiBOB (Lithium bis(oxalato)borate, LiB(CO)), and LiBETI (Lithium bisperfluoroethanesulfonimide, LiN(SOCFCF)). The second lithium salt may be the same as or different from the first lithium salt. More specifically, the second lithium salt may include at least one of LiPF, LiFSI, LiTFSI, LiBOB, and LiBETI. Preferably, the second lithium salt has a relatively high metal oxidation power compared to the first lithium salt, but a relatively high ionic conductivity, which can reduce internal electrical resistance and improve thermal stability when the battery cell is exposed to a high-temperature environment. To this end, LiPF6 can be used in combination with at least one of LiFSI, LiTFSI, LiBOB2, and LiBETI, which are different from the first lithium salt.

[0091] Meanwhile, when at least one of LiFSI, LiTFSI, LiBOB2, and LiBETI is used in combination with LiPF6 as the second lithium salt, the molar concentration ratio of LiPF6 to the lithium salt other than LiPF6 may be 1:1 to 1:6.7, specifically 1:1 to 1:4. In other words, when the molar concentration of LiPF6 is higher than the molar concentration of the lithium salt other than LiPF6, the ionic conductivity of the liquid electrolyte 160 decreases, and the internal resistance of the battery cell 100 becomes relatively increaseOn the other hand, if the molar concentration ratio of the lithium salt other than LiPF6 to LiPF6 exceeds 6.7, the manufacturing cost of the battery cell may increase. Therefore, by configuring the battery cell 100 according to the present invention so that the molar concentration ratio of the second lithium salt to the third lithium salt is 1:1 to 1:6.7, it is possible to reduce the increase in the internal electrical resistance of the battery cell 100 while increasing the amount of LiPF6, which is relatively inexpensive, and thereby reduce the manufacturing cost of the battery cell 100.

[0092] The organic solvent contained in the liquid electrolyte may be the same as or different from the organic solvent used in the gel electrolyte, and may be one or more selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), vinylene carbonate (VC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), and γ-butyrolactone. The organic solvent is not necessarily limited to the above-listed structures, and similar effects can be achieved by using known structures and their equivalents.

[0093] In addition, the liquid electrolyte may further contain additives as needed to further improve the high-rate discharge characteristics, high-temperature stability, overcharge prevention, and battery expansion suppression effects of the battery.

[0094] Examples of such additives include at least one selected from the group consisting of non-fluorine-substituted cyclic carbonate compounds, sultone compounds, sulfate compounds, benzene compounds, amine compounds, and silane compounds.

[0095] Examples of the cyclic carbonate compound not substituted with fluorine include vinylene carbonate (VC) and vinylethylene carbonate (VEC).

[0096] Specific examples of the sultone compound include at least one selected from the group consisting of 1,3-propane sultone (PS), 1,4-butane sultone, ethene sultone, 1,3-propene sultone (PRS), 1,4-butene sultone, and 1-methyl-1,3-propene sultone.

[0097] Specific examples of the sulfate-based compound include ethylene sulfate (Esa), trimethylene sulfate (TMS), and methyl trimethylene sulfate (MTMS).

[0098] The benzene-based compound may be fluorobenzene, and the amine-based compound may be triethanolamine or ethylenediamine. The silane-based compound may be tetravinylsilane or the like.

[0099] The additive may be a mixture of two or more compounds and may be included in an amount of 0.01 wt% to 20 wt%, specifically 0.05 wt% to 5 wt%, based on the total weight of the liquid electrolyte. If the content of the additive exceeds 20 wt%, excessive side reactions may occur during charging and discharging of the battery due to the excess additive.

[0100] Meanwhile, the viscosity of the liquid electrolyte 160 may be 2 cP to 20 cP. When the viscosity is within this range, the electrolyte 160 can have an appropriate viscosity that allows it to uniformly and thoroughly permeate the electrodes 122, thereby improving the initial charge / discharge efficiency of the battery cell 100, shortening the manufacturing time of the battery cell 100, and effectively reducing manufacturing costs.

[0101] On the other hand, if the viscosity of the liquid electrolyte 160 is less than 2 cP, the capacity and life of the battery cell 100 may be reduced. Conversely, if the viscosity of the liquid electrolyte 160 is more than 20 cP, 160 This may decrease the wettability of the battery cell 100, increase the manufacturing time, and increase the manufacturing cost of the battery cell 100.

[0102] Meanwhile, in the battery cell 100 of the present invention, as the battery cell 100 is repeatedly charged and discharged, the amount of available lithium salt participating in the charge and discharge of the liquid electrolyte 160 gradually decreases due to lithium precipitation, etc. However, due to the lithium salt concentration gradient between the gel electrolyte 150 and the liquid electrolyte 160, the first lithium salt in the gel electrolyte 150, which is the solute, moves to the liquid electrolyte 160, thereby replenishing the depleted lithium salt in the liquid electrolyte 160. As a result, even though the battery cell 100 of the present invention is manufactured using a liquid electrolyte 160 with a relatively low concentration, the depletion of available lithium salt participating in the charge and discharge of the liquid electrolyte 160 can be prevented even when the battery cell 100 is charged and discharged multiple times, thereby effectively extending the life of the battery cell 100. This effect is demonstrated in the experimental examples described below. Meanwhile, the method for manufacturing a battery cell of the present invention will be described in more detail below.

[0103] Battery cell manufacturing method According to one embodiment of the present invention, the method for manufacturing a battery cell of the present invention includes the steps of: preparing an electrode assembly including a plurality of electrodes, electrode tabs formed on at least one side of each of the plurality of electrodes, and separators interposed between the plurality of electrodes; placing the electrode assembly in an accommodating space of a cell case; a gel electrolyte composition including a first lithium salt having a first molar concentration and a curable compound is injected into the receiving space, and then the gel electrolyte composition is disposed around the electrode tab; curing the gel electrolyte composition to form a gel electrolyte surrounding the electrode tabs; and injecting a liquid electrolyte containing a second lithium salt at a second molar concentration so as to be contained between the plurality of electrodes.

[0104] First, based on FIGS. 1, 4, and 5, FIGS. 6 to 11 show a manufacturing method for manufacturing the battery cell 100 of the present invention. First, a method for manufacturing a battery cell 100 according to an embodiment of the present invention may include the steps of: preparing an electrode assembly including a plurality of electrodes 122p, 122n, electrode tabs 121 formed on at least one side of each of the plurality of electrodes 122p, 122n, and a separator interposed between the plurality of electrodes 122p, 122n; disposing the electrode assembly 120 in an accommodating space 110p1 of a cell case 110; injecting a gel electrolyte composition including a first lithium salt with a first molar concentration and a curable compound into the accommodating space 110p1 so as to surround the electrode tabs; curing the gel electrolyte composition to prevent movement of the electrode tabs 121, and disposing the gel electrolyte around the electrode tabs; and injecting a liquid electrolyte 160 including a second lithium salt with a second molar concentration to be accommodated between the plurality of electrodes 122p, 122n.

[0105] In this case, the step of preparing the electrode assembly 120 may include a step of sequentially stacking a positive electrode 122p having a positive electrode tab 121a formed on one side thereof, a separator 170, and a negative electrode 122n having a negative electrode tab 121b formed on one side thereof to form the electrode assembly 120. In this case, the electrodes 122p and 122n may each have an electrode tab 121 formed on at least one side thereof.

[0106] In one embodiment, the step of placing the electrode assembly 120 in the receiving space 110p1 of the pouch 114 includes placing the electrode assembly 120, which includes electrodes 122 with electrode tabs 121 formed on at least one side thereof and a separator 170 interposed between the electrodes 122, in the receiving space 110p1 of the pouch 114. Here, the pouch 114 can be considered a configuration prior to manufacturing the cell case 110 in which the receiving space 110p1 is completely sealed. The pouch 114 may be formed by joining the outer peripheries of the first cell sheet 114T and the second cell sheet 114P to each other. The pouch 114 may have a receiving space 110p1 capable of containing the electrode tabs 121, the electrode assembly 120, the gel electrolyte composition 155, and the liquid electrolyte 160.

[0107] For example, the electrode tab 121 may be located on the first side 120a of the electrode assembly 120. However, this is not necessarily limited to this configuration, and a battery cell (not shown) manufactured by a manufacturing method according to another embodiment may have the electrode tabs 121 located on both the first side 120a and the third side 120c of the electrode assembly 120. In this case, the gel electrolyte 150 may be disposed on both the first side 120a and the third side 120c of the electrode assembly 120 within the receiving space 110p1 of the pouch 114. In this case, the liquid electrolyte 160 may be located between the electrodes 122 and the separator 170, between the electrodes 122, and on the second side 120b and the fourth side 120d of the electrode assembly 120 within the receiving space 110p1.

[0108] Therefore, according to this configuration of the present invention, the manufacturing method of the present invention makes it possible to manufacture a battery cell 100 that can effectively prevent disconnection at the connection portion between the electrode tab 121 and the electrode 122 or at the bent portion of the electrode tab 121, by preventing the electrode tab 121 from moving due to the gel electrolyte 150 surrounding the electrode tab 121, compared to when the liquid electrolyte 160 of the conventional battery cell 100 surrounds the electrode tab 121.

[0109] In addition, the manufacturing method of the present invention allows the manufactured battery cell 100 to form a passivation film 123 on the surface of the electrode tab 121, which can prevent the electrode tab 121 from breaking due to corrosion of the electrode tab 121 caused by lithium salt contained in the electrolyte of conventional battery cells, thereby effectively improving the durability of the battery cell 100.

[0110] Specifically, FIG. 6 shows a front view of a method for manufacturing a battery cell 100 according to another embodiment of the present invention, in which multiple electrodes 122p, 122n are inserted into the storage space 110p1 of the pouch 114.

[0111] 7 is a front view showing the interior of a pouch in which the above-described gel electrolyte composition 155 is being poured into the containing space 110p1 in a method for manufacturing a battery cell 100 according to another embodiment of the present invention. For reference, in FIG. 7, for ease of explanation, the pouch 114 is shown as transparent so that the interior of the pouch 114 can be seen from the outside.

[0112] 6, after inserting an electrode assembly (not shown) into the cell sheet storage space 110p1, the first cell sheet 114T and the second cell sheet 114P are stacked to form the pouch 114. The first outer periphery 114a, the third outer periphery 114c, and the fourth outer periphery 114d are heat-sealed to each other except for a portion of the outer periphery, for example, the second outer periphery 114b, to form the sealed portion 111. Furthermore, the first cell sheet 114T and the second cell sheet 114P are configured to be separated from each other by the second outer periphery 114b, allowing the gel electrolyte composition 155 or the liquid electrolyte 160 to flow into the storage space 110p1 without being heat-sealed.

[0113] 2, 5, and 7, an injection space 110p2 may be formed in the second outer peripheral portion 114b by the heat sealing process of the outer peripheral portion. The injection space 110p2 may be a space located on one side (upper side) of the receiving space 110p1, in which the electrode 122 is received, among the internal spaces formed between the first cell sheet 114T and the second cell sheet 114P. For example, the injection space 110p2 may be defined as a region from the open second outer peripheral portion 114b of the pouch 114 to the front of the receiving space 110p1. The injection space 110p2 may be configured to communicate with the receiving space 110p1. The injection space 110p2 may serve as a passageway for the gel electrolyte composition 155 or the liquid electrolyte 160 to move into the receiving space 110p1.

[0114] Referring to FIG. 7, the method for manufacturing the battery cell 100 of the present invention may further include a step of heat-sealing a portion between the injection space 110p2 and the storage space 110p1 of the pouch 114 to form a blocking portion 113 before injecting the gel electrolyte composition.

[0115] The blocking portion 113 may be formed by heat sealing from the first outer periphery 114a to the third outer periphery 114c of the pouch 114. Such a blocking section can prevent the gel electrolyte composition injected into the accommodation space from moving back to the injection space before it hardens, and can easily maintain the state in which the gel electrolyte composition is arranged to surround the electrode tab until the gel electrolyte composition hardens, thereby significantly improving the efficiency of the manufacturing process.

[0116] Referring to FIG. 7 together with FIG. 3, a gel electrolyte composition 155 containing the first lithium salt of the first molar concentration and a curable compound is injected into the receiving space 110p1 through the injection space 110p2 so as to surround the electrode tab 121.

[0117] The gel electrolyte composition 155 may be configured to be a liquid electrolyte before curing, and to change from the liquid electrolyte to a gel phase electrolyte by curing the curable compound in a subsequent step. After injection, the gel electrolyte composition 155 may be disposed in the receiving space 110p1 so as to surround the outer surfaces of the electrode tabs 121 or fill the spaces between the electrode tabs 121.

[0118] 8 is a front view showing the state inside the pouch where the gel electrolyte composition 155 is thermally cured in the containing space 110p1 in the manufacturing method of the battery cell 100 of the present invention. For reference, in FIG. 8, for ease of explanation, the pouch 114 is shown as transparent so that the state inside the pouch 114 can be seen from the outside.

[0119] 8, the step of changing the gel electrolyte composition 155 into the gel electrolyte 150 in a gel phase so as to prevent the electrode tabs 121 from moving includes the step of injecting the gel electrolyte composition 155 into the receiving space 110p1 so as to surround the electrode tabs 121, and then rotating the pouch 114 so that the electrode tabs 121 face downward. That is, the gel electrolyte composition 155 can move by gravity so as to surround the electrode tabs 121.

[0120] In one embodiment, the curing step may include curing the gel electrolyte composition 155, which is disposed in the accommodation space 110p1 so as to surround the electrode tab 121, into a gel phase. For example, if the gel electrolyte composition 155 contains a thermosetting compound, the gel electrolyte composition 155 may be thermally cured by storing the gel electrolyte composition 155 in a thermostatic bath set at a predetermined temperature for a predetermined period of time. The thermosetting compound is heated to form crosslinks through a thermal polymerization reaction, and the gel electrolyte composition 155 may be converted from a liquid state into a gel state. For example, when storing the pouch 114 in a thermostatic bath, the pouch 114 may be stored in the thermostatic bath at 60°C for 5 to 24 hours to convert the gel electrolyte composition 155 into a gel state.

[0121] Therefore, according to this configuration of the present invention, the method for manufacturing a battery cell 100 can manufacture a battery cell 100 in which the gel electrolyte 150 prevents the electrode tabs 121 from flowing and reduces deformation when an external impact is applied to the battery cell 100, compared to the conventional battery cell 100 in which the liquid electrolyte 160 surrounds the electrode tabs 121. As a result, the method for manufacturing a battery cell 100 of the present invention can effectively improve the durability of the battery cell 100.

[0122] Fig. 9 is a side view showing a state before the battery cell 100 is fixed using a fixing jig 210 while the gel electrolyte composition 155 is curing in the battery cell manufacturing method according to the present invention. Fig. 10 is a side view showing a state after the battery cell 100 has been fixed using the fixing jig 210 while the gel electrolyte composition 155 is curing in the battery cell manufacturing method according to the present invention. For ease of explanation, electrode tabs 121 and the like are not shown in Figs. 9 and 10.

[0123] 9 and 10 , in the step of injecting the gel electrolyte composition 155 containing the curable compound into the accommodation space 110p1 so as to surround the electrode tab 121, when the gel electrolyte composition 155 is injected into the pouch 114, a portion of the accommodation space 110p1 of the pouch 114 containing the gel electrolyte composition 155 may be deformed into a convex shape toward the outside due to the fluidity of the gel electrolyte composition 155. When the gel electrolyte composition 155 is cured to have a shape in which a portion of the accommodation space 110p1 of the pouch 114 is deformed into a convex shape, the shape of the deformation may vary from product to product, making it difficult to ensure consistent product quality and causing defects such as an uneven appearance of the pouch 114.

[0124] Therefore, in the manufacturing method of the present invention, the step of converting the gel electrolyte composition 155 into the gel-phase gel electrolyte 150 to prevent the electrode tab 121 from flowing may include a step of pressurizing and fixing the pouch 114 while the gel electrolyte composition 155 hardens. In this case, the pouch 114 may be fixed by applying pressure to both outer sides using a fixing jig 210. Specifically, the fixing jig 210 may include a first fixing plate 212 and a second fixing plate 213. The first fixing plate 212 and the second fixing plate 213 may each have a size corresponding to or larger than one side of the pouch 114. That is, the first fixing plate 212 and the second fixing plate 213 may each have a size sufficient to cover the pouch 114. The pouch 114 and the electrode assembly 120 housed inside the pouch 114 may be interposed between the first fixing plate 212 and the second fixing plate 213. A portion of the accommodation space 110p1 of the pouch 114 that has been deformed into a convex shape can be pressurized by the first jig plate 212 and the second jig plate 213.

[0125] The fixing jig 210 may further include a receiving base 211, a first support 214, and a second support 215. The first support 214 and the second support 215 may be located on both sides (Y-axis direction) of the pouch 114. The receiving base 211 may be configured to be mounted on the ground so that the fixing jig 210 can be stably positioned on the ground. The receiving base 211 may have a plate shape extending parallel to the ground. For example, as shown in FIG. 12 , the first support 214 may include a pillar portion 214a extending upward (Z-axis direction) from the upper surface of the receiving base 211, and a connecting portion 214b extending horizontally from the pillar portion 214a and connected to the side of the first jig plate 212 in the positive direction of the Y-axis. The second support 215 may also include a pillar portion 215a extending upward from the upper surface of the receiving base 211, and a connecting portion 215b extending horizontally from the pillar portion 215a and connected to the side of the second jig plate 213 facing in the negative direction of the Y axis.

[0126] Furthermore, the first support 214 and the second support 215 may be configured to be movable toward or away from each other on the receiving table 211. For example, when the first support 214 and the second support 215 move toward each other, the first jig plate 212 and the second jig plate 213 connected to the first support 214 and the second support 215, respectively, may move toward each other. In this case, the pouch 114 and the electrode assembly 120 housed in the pouch 114 may be fixed by applying pressure to both outer sides of the pouch 114 located between the first jig plate 212 and the second jig plate 213. For example, when the hardening of the gel electrolyte composition 155 is completed, the first support 214 and the second support 215 may be moved away from each other to release the fixed state of the pouch 114. 9, the pouch 114 may have a shape in which a portion of the storage space 110p1 of the pouch 114 protrudes convexly due to the gel electrolyte composition 155. However, as shown in FIG. 10, when the first support 214 and the second support 215 move toward the pouch 114, the pouch 114 is pressurized by the first jig plate 212 and the second jig plate 213, and this pressure can guide the storage space 110p1, which has become convex due to the gel electrolyte composition 155, to deform into a recessed shape.

[0127] Therefore, according to this configuration of the present invention, the manufacturing method of the present invention includes a step of pressurizing and fixing the pouch 114 while the gel electrolyte composition 155 is hardening to prevent the electrode tab 121 from moving, thereby stably fixing the electrode assembly 120 contained inside the pouch 114 and preventing the gel electrolyte composition 155 from solidifying in a state in which a portion of the containing space 110p1 of the pouch 114 is deformed outwardly into a convex shape due to the gel electrolyte composition 155. As a result, the manufacturing method of the present invention can effectively reduce the defective rate of the manufactured battery cells 100.

[0128] 11 is a perspective view showing the interior of pouch 114 in which liquid electrolyte 160 is being injected into housing space 110p1 in a battery cell manufacturing method according to the present invention. For reference, in FIG. 11, for ease of explanation, pouch 114 is shown as transparent so that the interior of pouch 114 can be seen from the outside.

[0129] 2, 4, 8, and 11, the method for manufacturing a battery cell according to the present invention may further include a step of rotating the electrode assembly 120 so that the electrode tab 121 is positioned in the X-axis direction before the step of injecting the liquid electrolyte 160. In this case, the pouch 114 may be in a vertical position (Z-axis direction) relative to the ground in FIG. 11 so that the receiving space 110p1 is visible from the front relative to the ground. In this case, because the gel electrolyte composition 155 has already changed into a gel phase to form the gel electrolyte 150, even when the pouch 114 is rotated so that the electrode tab 121 is positioned at the side (X-axis direction) of the electrode assembly 120, the gel electrolyte 150 does not move to another position in the receiving space 110p1. In addition, the liquid electrolyte 160 may be filled into the remaining space of the receiving space 110p1 where the gel electrolyte 150 is not positioned.

[0130] Specifically, the step of injecting the liquid electrolyte 160 may include injecting the liquid electrolyte 160 into the receiving space 110p1 through the injection space 110p2 via the open second outer peripheral portion 114b of the first cell sheet 114T and the second cell sheet 114P. In this case, the liquid electrolyte 160 may be positioned between the electrodes 122 and surrounding the other side of the electrodes 122 where the electrode tabs 121 are not positioned. For example, the liquid electrolyte 160 may be positioned between the electrodes 122 and on the outermost side of the electrodes 122. Also, as shown in FIG. 11 , the liquid electrolyte 160 may be positioned to surround the second side 120b, the third side 120c, and the fourth side 120d of the electrode assembly 120.

[0131] In addition, the method for manufacturing a battery cell of the present invention injects highly fluid liquid electrolyte 160 containing a second lithium salt with a second molar concentration lower than that of gel electrolyte 150, thereby shortening the time required for absorption into the electrodes of electrode assembly 120 and improving the wettability of the electrodes, thereby improving the initial charge / discharge efficiency, shortening the manufacturing time for battery cell 100, and effectively reducing manufacturing costs.

[0132] Fig. 12 is a front view showing a state in which one side of the containing space 110p1 of the pouch 114 has been further sealed in the battery cell manufacturing method according to the present invention. Fig. 13 is a front view showing a state in which the injection space 110p2 of the pouch 114 has been removed in the battery cell manufacturing method according to the present invention.

[0133] 12 and 13, together with FIG. 4, the method for manufacturing a battery cell 100 according to the present invention may further include the steps of sealing the receiving space 110p1 of the pouch 114 and cutting the region of the injection space 110p2. Specifically, the step of sealing the receiving space 110p1 of the pouch 114 may involve heat sealing the entire boundary between the receiving space 110p1 and the injection space 110p2 of the pouch 114. For example, as shown in FIG. 12, the seal portion 111 may be formed by heat sealing from the first outer periphery 114a to the third outer periphery 114c of the pouch 114 along the boundary between the receiving space 110p1 and the injection space 110p2 of the pouch 114. For example, in the manufacturing method of the battery cell 100 of Figure 7 described above, if a portion between the injection space 110p2 and the storage space 110p1 of the pouch 114 is heat-sealed to form the blocking portion 113, the blocking portion 113 can be heat-sealed to the third outer peripheral portion 114c of the pouch 114 to further form the sealing portion 111.

[0134] Also, a cutting line (L) can be set on the outside of the seal portion 111. Thereafter, as shown in Fig. 13, the region of the injection space 110p2 of the pouch 114 can be removed by cutting along the cutting line (L).

[0135] Furthermore, in a manufacturing method according to another embodiment of the present invention, a battery activation process may be performed before the step of sealing the receiving space 110p1 of the pouch 114, which is performed in FIG. 12 . Here, the battery activation process is a process in which the battery cell 100 is first charged / discharged. A large amount of gas is generated during the charge / discharge operation of the battery cell 100. This generated gas moves from the receiving space 110p1 to the injection space 110p2 and can be discharged to the outside through the open second outer peripheral portion 114b of the pouch 114. In this battery activation process, the magnitude of the charging current and the charging / discharging time may vary depending on the materials of the positive electrode 122p and the negative electrode 122n.

[0136] Furthermore, in the manufacturing method according to the present invention, a battery aging process may be performed after the step of sealing the receiving space 110p1 of the pouch 114. In this case, the temperature may be, for example, 45 to 70 degrees Celsius, and the aging time may be 1 to 3 days.

[0137] The battery cell 100 manufactured by the manufacturing method of the present invention as described above has a gel electrolyte 150 with low fluidity disposed in a manner surrounding the electrode tab 121, thereby preventing movement and deformation of the electrode tab 121 due to external impact, compared to a battery cell 100 in which a conventional liquid electrolyte 160 surrounds the electrode tab 121. Therefore, when the battery cell 100 of the present invention is applied to an automobile, even if the battery cell 100 is subjected to frequent impacts and vibrations that occur during movement, the gel electrolyte 150 minimizes movement of the electrode tab 121, preventing disconnection, thereby extending the lifespan and preventing inactivation of the electrodes 122 and reducing reduction in battery capacity.

[0138] The battery cell 100 manufactured by the manufacturing method of the present invention as described above maximizes the amount of fluid liquid electrolyte 160 in the space between the accommodation space 110p1 and the electrode assembly 120, and also includes a gel electrolyte 150 containing a first lithium salt at a first molar concentration that is higher than the second concentration of the second lithium salt in the liquid electrolyte 160. Therefore, even if the second lithium salt in the liquid electrolyte 160 decreases due to repeated charging and discharging, the first lithium salt moves from the gel electrolyte 150, which is a solute, to the liquid electrolyte 160 due to the concentration gradient of the lithium salt with the gel electrolyte 150, and replenishes the deficient lithium salt in the liquid electrolyte 160. This prevents the depletion of the lithium salt in the liquid electrolyte 160 and effectively extends the life of the battery cell 100.

[0139] Meanwhile, FIG. 14 is a perspective view that schematically shows the state of a battery module 1000 according to one embodiment of the present invention. 14 together with FIG. 1, the present invention may provide a battery module 1000 including at least one battery cell 100. The battery module 1000 may include a module housing 1100 that accommodates the at least one battery cell 100 therein, an external output terminal 1200 provided at the front end of the module housing 1100, and a controller 1300 that controls charging and discharging of the battery cell 100. In addition, if two or more battery cells 100 are provided, the battery module 1000 may further include a bus bar (not shown) that electrically connects the two or more battery cells 100. The bus bar may be electrically connected to the electrode leads 130 of each battery cell 100. The battery module 1000 of the present invention may employ known configurations for essential components other than the battery cell 100, and therefore, description of such components will be omitted.

[0140] Hereinafter, the present invention will be described in detail with reference to examples. However, the examples of the present invention may be modified in various different forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0141] Example Example 1 (Production of liquid electrolytes) A liquid electrolyte was prepared by dissolving LiPF6 at a concentration of 0.75M in a non-aqueous organic solvent consisting of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70, and then adding 1 wt% vinylene carbonate (VC) as an additive. The viscosity of the liquid electrolyte was 2.5 cP.

[0142] (Production of gel electrolyte composition) LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC):ethyl methyl carbonate (DMC) in a volume ratio of 30:70 to a molar concentration of 2.0 M. Then, 5 wt% of trimethylolpropane triacrylate (as a curable polymer), 1 wt% of 2,2'-azobis(isobutyronitrile) (AIBN) as a polymerization initiator, and 1 wt% of vinylene carbonate (VC) were added to prepare a gel electrolyte composition. The viscosity of the gel electrolyte composition was 8.0 cP.

[0143] (Manufacturing of electrode assemblies) Cathode active material (Li(Ni) 0.8 Co 0.1 Mn 0.1A cathode active material slurry (solid content: 48 wt%) was prepared by adding a 94:3:3 weight ratio of carbon dioxide (CO2), a conductive material (carbon black), and a binder (polyvinylidene fluoride: PVDF) to N-methyl-2-pyrrolidone (NMP) as a solvent. The cathode active material slurry was applied to a 15 μm-thick cathode current collector (Al thin film), dried, and then roll-pressed to prepare a cathode. Anode active material slurry (solid content: 70 wt%) was prepared by adding a 96:2:1:1 weight ratio of carbon dioxide (CO2), a binder (styrene-butadiene rubber, SBR), sodium carboxymethyl cellulose (CMC), and a conductive material (carbon black) to water as a solvent. The negative electrode active material slurry was applied to a 10 μm-thick negative electrode current collector (Cu thin film), dried, and then roll-pressed to fabricate a negative electrode. An electrode assembly was fabricated by stacking the positive electrode, a three-layer separator made of polypropylene / polyethylene / polypropylene (PP / PE / PP), and a negative electrode.

[0144] (battery cell manufacturing) After preparing the electrode assembly manufactured by the above method, it was placed in a pouch, and the gel electrolyte composition prepared above was poured into the storage space so as to surround the electrode tab. The pouch was then stored at a high temperature of 60°C for 5 hours in a thermostatic chamber to thermally harden the gel electrolyte composition into a gel electrolyte. Next, the liquid electrolyte prepared above was poured into the storage space of the pouch so as to impregnate the electrode assembly, and the pouch was sealed to manufacture a battery cell. At this time, the volume ratio of the liquid electrolyte to the gel electrolyte composition poured into the pouch was approximately 100:25.

[0145] Example 2 (Production of liquid electrolytes) LiPF6 and LiN(SO2F)2 (LiFSI) were dissolved in a non-aqueous organic solvent (ethylene carbonate (EC): ethyl methyl carbonate (EMC)) in a volume ratio of 30:70 to make 0.3M and 0.7M, respectively. Then, 1 wt% vinylene carbonate (VC) was added to prepare a liquid electrolyte. The viscosity of the liquid electrolyte was 3.4 cP.

[0146] (Production of gel electrolyte composition) LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC):ethyl methyl carbonate (DMC) in a volume ratio of 30:70 to a molar concentration of 2.0 M. Subsequently, 5 wt% of trimethylolpropane triacrylate was added as a curable polymer, and 1 wt% of 2,2'-azobis(isobutyronitrile) (AIBN) and 1 wt% of vinylene carbonate (VC) were added as polymerization initiators to prepare a gel electrolyte composition. The viscosity of the gel electrolyte was 8.0 cP.

[0147] (battery cell manufacturing) The electrode assembly prepared in Example 1 was housed in a pouch, and the gel electrolyte composition prepared above was poured into the housing space so as to surround the electrode tabs. The pouch was then stored in a thermostatic chamber at 60°C for 5 hours to thermally cure the gel electrolyte composition into a gel electrolyte.

[0148] The liquid electrolyte prepared above was then poured into the pouch so as to impregnate the electrode assembly, and the pouch was then sealed to prepare a battery cell. At this time, the volume ratio of the liquid electrolyte to the gel electrolyte composition poured into the pouch was approximately 100:25.

[0149] Example 3 (Production of liquid electrolytes) LiPF6 and LiN(SO2F)2 (LiFSI) were dissolved in a non-aqueous organic solvent (ethylene carbonate (EC): ethyl methyl carbonate (EMC)) in a volume ratio of 30:70 to make 0.7M and 0.7M, respectively. Then, 1 wt% vinylene carbonate (VC) was added to prepare a liquid electrolyte. The viscosity of the liquid electrolyte was 3.4 cP.

[0150] (battery cell manufacturing) A battery cell was manufactured in the same manner as in Example 2, except that the liquid electrolyte prepared above was poured into the storage space of the pouch. At this time, the volume ratio of the liquid electrolyte to the gel electrolyte composition poured into the pouch was about 100:25.

[0151] (battery cell manufacturing) The electrode assembly prepared in Example 1 was housed in a pouch, and the gel electrolyte composition prepared above was poured into the housing space so as to surround the electrode tabs. The pouch was then stored in a thermostatic chamber at 60°C for 5 hours to thermally cure the gel electrolyte composition into a gel electrolyte.

[0152] The liquid electrolyte prepared above was then poured into the pouch so as to impregnate the electrode assembly, and the pouch was then sealed to prepare a battery cell. At this time, the volume ratio of the liquid electrolyte to the gel electrolyte composition poured into the pouch was approximately 100:25.

[0153] Example 4 (Production of liquid electrolytes) LiPF6 and LiN(SO2F)2 (LiFSI) were dissolved in a non-aqueous organic solvent (ethylene carbonate (EC): ethyl methyl carbonate (EMC)) in a volume ratio of 30:70 to make 0.3M and 0.7M, respectively. Then, 1 wt% vinylene carbonate (VC) was added to prepare a liquid electrolyte. The viscosity of the liquid electrolyte was 3.4 cP.

[0154] (Production of gel electrolyte composition) LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC):ethyl methyl carbonate (DMC) in a volume ratio of 30:70 to a molar concentration of 5.0M. Subsequently, 5 wt% of trimethylolpropane triacrylate was added as a curable polymer, and 1 wt% of 2,2'-azobis(isobutyronitrile) (AIBN) and 1 wt% of vinylene carbonate (VC) were added as polymerization initiators to produce a gel electrolyte composition. The viscosity of the gel electrolyte was 34.0 cP.

[0155] (battery cell manufacturing) The electrode assembly prepared in Example 1 was housed in a pouch, and the gel electrolyte composition prepared above was poured into the housing space so as to surround the electrode tabs. The pouch was then stored in a thermostatic chamber at 60°C for 5 hours to thermally cure the gel electrolyte composition into a gel electrolyte.

[0156] The liquid electrolyte prepared above was then poured into the pouch so as to impregnate the electrode assembly, and the pouch was then sealed to prepare a battery cell. At this time, the volume ratio of the liquid electrolyte to the gel electrolyte composition poured into the pouch was approximately 100:25.

[0157] Example 5 (Production of liquid electrolytes) LiPF6 and LiN(SO2F)2 (LiFSI) were dissolved in a non-aqueous organic solvent (ethylene carbonate (EC): ethyl methyl carbonate (EMC)) in a volume ratio of 30:70 to make 0.3M and 0.7M, respectively. Then, 1 wt% vinylene carbonate (VC) was added to prepare a liquid electrolyte. The viscosity of the liquid electrolyte was 3.4 cP.

[0158] (Production of gel electrolyte composition) LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC):ethyl methyl carbonate (DMC) in a volume ratio of 30:70 to a molar concentration of 6.0M. Subsequently, 5 wt% of trimethylolpropane triacrylate was added as a curable polymer, and 1 wt% of 2,2'-azobis(isobutyronitrile) (AIBN) and 1 wt% of vinylene carbonate (VC) were added as polymerization initiators to produce a gel electrolyte composition. The viscosity of the gel electrolyte was 62.0 cP.

[0159] (battery cell manufacturing) The electrode assembly prepared in Example 1 was housed in a pouch, and the gel electrolyte composition prepared above was poured into the housing space so as to surround the electrode tabs. The pouch was then stored in a thermostatic chamber at 60°C for 5 hours to thermally cure the gel electrolyte composition into a gel electrolyte.

[0160] The liquid electrolyte prepared above was then poured into the pouch so as to impregnate the electrode assembly, and the pouch was then sealed to prepare a battery cell. At this time, the volume ratio of the liquid electrolyte to the gel electrolyte composition poured into the pouch was approximately 100:25.

[0161] Comparative Example 1 (Production of liquid electrolytes) A liquid electrolyte was prepared by dissolving LiPF6 at a concentration of 1.0 M in a non-aqueous organic solvent consisting of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70, and then adding 1 wt% vinylene carbonate (VC) as an additive. The viscosity of the liquid electrolyte was 3.3 cP.

[0162] (Production of gel electrolyte composition) LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC):ethyl methyl carbonate (DMC) in a volume ratio of 30:70 to a molar concentration of 1.0 M. Then, 5 wt% of trimethylolpropane triacrylate (as a curable polymer), 1 wt% of 2,2'-azobis(isobutyronitrile) (AIBN) as a polymerization initiator, and 1 wt% of vinylene carbonate (VC) were added to prepare a gel electrolyte composition. The viscosity of the gel electrolyte composition was 4.7 cP.

[0163] (battery cell manufacturing) The electrode assembly prepared in Example 1 was housed in a pouch, and the gel electrolyte composition prepared above was poured into the housing space so as to surround the electrode tabs. The pouch was then stored in a thermostatic chamber at 60°C for 5 hours to thermally cure the gel electrolyte composition into a gel electrolyte.

[0164] The liquid electrolyte prepared above was then poured into the pouch so as to impregnate the electrode assembly, and the pouch was then sealed to prepare a battery cell. At this time, the volume ratio of the liquid electrolyte to the gel electrolyte composition poured into the pouch was approximately 100:25.

[0165] Comparative Example 2 (Production of liquid electrolytes) A liquid electrolyte was prepared by dissolving LiPF6 at a concentration of 0.5M in a non-aqueous organic solvent consisting of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70, and then adding 1 wt% vinylene carbonate (VC) as an additive. The viscosity of the liquid electrolyte was 1.7 cP.

[0166] (Production of gel electrolyte composition) LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC):ethyl methyl carbonate (DMC) in a volume ratio of 30:70 to a molar concentration of 0.5M. Then, 5 wt% of trimethylolpropane triacrylate (as a curable polymer), 1 wt% of 2,2'-azobis(isobutyronitrile) (AIBN) as a polymerization initiator, and 1 wt% of vinylene carbonate (VC) were added to prepare a gel electrolyte composition. The viscosity of the gel electrolyte composition was 2.0 cP.

[0167] (battery cell manufacturing) The electrode assembly prepared in Example 1 was housed in a pouch, and the gel electrolyte composition prepared above was poured into the housing space so as to surround the electrode tabs. The pouch was then stored in a thermostatic chamber at 60°C for 5 hours to thermally cure the gel electrolyte composition into a gel electrolyte.

[0168] The liquid electrolyte prepared above was then poured into the pouch so as to impregnate the electrode assembly, and the pouch was then sealed to prepare a battery cell. At this time, the volume ratio of the liquid electrolyte to the gel electrolyte composition poured into the pouch was approximately 100:25.

[0169] Comparative Example 3 (Production of liquid electrolytes) A liquid electrolyte was prepared by dissolving LiPF6 at a concentration of 2.0 M in a non-aqueous organic solvent consisting of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70, and then adding 1 wt% vinylene carbonate (VC) as an additive. The viscosity of the liquid electrolyte was 6.7 cP.

[0170] (Production of gel electrolyte composition) LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC):ethyl methyl carbonate (DMC) in a volume ratio of 30:70 to a molar concentration of 2.0 M. Then, 5 wt% of trimethylolpropane triacrylate (as a curable polymer), 1 wt% of 2,2'-azobis(isobutyronitrile) (AIBN) as a polymerization initiator, and 1 wt% of vinylene carbonate (VC) were added to prepare a gel electrolyte composition. The viscosity of the gel electrolyte composition was 8.0 cP.

[0171] (battery cell manufacturing) The electrode assembly prepared in Example 1 was housed in a pouch, and the gel electrolyte composition prepared above was poured into the housing space so as to surround the electrode tabs. The pouch was then stored in a thermostatic chamber at 60°C for 5 hours to thermally cure the gel electrolyte composition into a gel electrolyte.

[0172] The liquid electrolyte prepared above was then poured into the pouch so as to impregnate the electrode assembly, and the pouch was then sealed to prepare a battery cell. At this time, the volume ratio of the liquid electrolyte to the gel electrolyte composition poured into the pouch was approximately 100:25.

[0173] Comparative Example 4 (Production of liquid electrolytes) A liquid electrolyte was prepared by dissolving LiN(SO2F)2 at a concentration of 1.0 M in a non-aqueous organic solvent consisting of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70, and then adding 1 wt% vinylene carbonate (VC) as an additive. The viscosity of the liquid electrolyte was 3.5 cP.

[0174] (Production of gel electrolyte composition) LiN(SO2F2)2 was dissolved to a concentration of 1.0 M in a non-aqueous organic solvent containing ethylene carbonate (EC):ethyl methyl carbonate (DMC) in a volume ratio of 30:70. Then, 5 wt% of trimethylolpropane triacrylate (as a curable polymer), 1 wt% of 2,2'-azobis(isobutyronitrile) (AIBN) as a polymerization initiator, and 1 wt% of vinylene carbonate (VC) were added to prepare a gel electrolyte composition. The viscosity of the gel electrolyte was 5.0 cP.

[0175] (battery cell manufacturing) A battery cell was manufactured in the same manner as in Example 1, except that the liquid electrolyte and gel electrolyte compositions prepared above were injected. At this time, the volume ratio of the liquid electrolyte and gel electrolyte compositions injected into the pouch was about 100:25.

[0176] Comparative Example 5 (Production of liquid electrolytes) A liquid electrolyte was prepared by dissolving LiPF6 and LiN(SO2F)2 at 0.7M and 0.3M, respectively, in a non-aqueous organic solvent consisting of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70. Then, vinylene carbonate (VC) was added at 1 wt% as an additive, resulting in a viscosity of 3.4 cP.

[0177] (Production of gel electrolyte composition) LiPF6 and LiN(SO2F)2 were dissolved in a non-aqueous organic solvent (ethylene carbonate (EC): ethyl methyl carbonate (DMC) mixed at a volume ratio of 30:70) to 0.7M and 0.3M, respectively. Then, 5 wt% of trimethylolpropane triacrylate (as a curable polymer), 1 wt% of 2,2'-azobis(isobutyronitrile) (AIBN) as a polymerization initiator, and 1 wt% of vinylene carbonate (VC) were added to prepare a gel electrolyte composition. The viscosity of the gel electrolyte was 4.8 cP.

[0178] (battery cell manufacturing) The electrode assembly prepared in Example 1 was housed in a pouch, and the gel electrolyte composition prepared above was poured into the housing space so as to surround the electrode tabs. The pouch was then stored in a thermostatic chamber at 60°C for 5 hours to thermally cure the gel electrolyte composition into a gel electrolyte.

[0179] The liquid electrolyte prepared above was then poured into the pouch so as to impregnate the electrode assembly, and the pouch was then sealed to prepare a battery cell. At this time, the volume ratio of the liquid electrolyte to the gel electrolyte composition poured into the pouch was approximately 100:25.

[0180] Experimental Example Experimental example 1: Evaluation of wettability of liquid electrolyte The time from when 1 ml of the liquid electrolyte applied to each of Example 1, Comparative Example 1, and Comparative Examples 3 to 5 was dropped onto the surface of the negative electrode using a dropper until the liquid electrolyte was completely absorbed into the negative electrode was measured, and the results are shown in Table 1 below. The shorter the measured time, the better the wettability can be evaluated.

[0181] [Table 1]

[0182] Referring to Table 1, it can be seen that the liquid electrolyte of Example 1 of the present invention has a low concentration of the second lithium salt and a low viscosity, and therefore has relatively better electrode wettability than the liquid electrolytes of Comparative Examples 1, 3 to 5.

[0183] Experimental example 2: Evaluation of internal resistance Five battery cells each were prepared for Examples 2 to 5 and Comparative Examples 1 to 5. A current of 2.5 C was passed through each electrode lead for 10 seconds, and the voltage drop was measured. The internal resistance was then calculated using the following formula (1). Here, "internal resistance" refers to output resistance in electrochemical evaluation. Next, the average internal resistance of each battery cell was calculated based on the average internal resistance of the battery cell of Comparative Example 1, and the average change in internal resistance was expressed as a percentage (%). This is shown in Table 2 below. Equation (1): R=V / I, where R is resistance, V is potential, and I is current.

[0184] [Table 2]

[0185] Referring to Table 2, it can be seen that the battery cells of Examples 2 to 5 of the present invention and the battery cell of Comparative Example 3 have a higher concentration of total lithium salts contained in the electrolyte than the battery cell of Comparative Example 1, and therefore the internal resistance is lower than that of the battery cell of Comparative Example 1. In particular, it can be seen that the rate of change in internal resistance of the battery cell of Example 5, which has the highest concentration of total lithium salts, is the lowest.

[0186] On the other hand, it can be seen that the battery cell of Comparative Example 5, by using a combination of LiPF6, which has high resistance, and LiFSI, which has low resistance, as lithium salts in the electrolyte, had a lower internal resistance than the battery cell of Comparative Example 1. Also, in the case of the battery cell of Comparative Example 4, it can be seen that the internal resistance was lower than that of Comparative Example 1 by excluding the use of LiPF6, which has high resistance, as a lithium salt in the electrolyte.

[0187] In contrast, the battery cell of Comparative Example 2 exhibited a significant increase in internal resistance compared to the battery cell of Comparative Example 1 due to a decrease in the concentration of all lithium salts contained in the entire electrolyte, resulting in a decrease in the mobility of lithium ions.

[0188] Experimental example 3: Evaluation of battery cell life characteristics To evaluate the life characteristics of the battery cells manufactured in Examples 1 to 5 and Comparative Examples 2 to 5, each battery cell was fixed using a fixture and subjected to 300 charge / discharge cycles in a 45°C ambient temperature environment within a driving voltage range of 2.5 V to 4.2 V, with a charge current (0.33 C, cut-off current: 1 / 20 C) and a discharge current (0.33 C). The difference between the charge capacity and discharge capacity of the battery cell in the first charge / discharge cycle was taken as the charge / discharge efficiency (%) and is shown in Table 3 below. The charge / discharge cycle efficiencies of the battery cells after 100 charge / discharge cycles and after 300 charge / discharge cycles were measured and are shown in Table 3 below.

[0189] [Table 3]

[0190] Referring to Table 3, the battery cells of Examples 1 to 4 of the present invention have a 100-cycle charge / discharge cycle efficiency of about 98.3% or more and a 300-cycle charge / discharge cycle efficiency of about 94.7% or more. That is, as charge / discharge proceeds, the first lithium salt in the gel electrolyte migrates to the liquid electrolyte through the interface between the gel electrolyte and the liquid electrolyte, thereby replenishing the lithium salt consumed in the liquid electrolyte, which is believed to result in excellent long-term and short-term life characteristics.

[0191] On the other hand, in the case of the battery cell of Example 5, the gel electrolyte composition contained a slightly large amount of lithium salt, which increased the viscosity of the gel electrolyte composition, reducing the fluidity of the gel electrolyte composition and making it difficult to move the gel electrolyte composition into the storage space around the electrode tab. As a result, the liquid electrolyte permeated into the storage space where the tab was formed, causing disconnection of the tab and slightly deteriorating the cycle characteristics.

[0192] In the case of the battery cell of Comparative Example 2, the low lithium salt concentration results in excellent impregnation of the liquid electrolyte and gel electrolyte, and therefore the initial charge-discharge cycle is superior to that of the Examples. However, as the charge-discharge cycle progresses, the lithium salt becomes increasingly depleted, and the charge-discharge cycle efficiency decreases.

[0193] In the case of the battery cell of Comparative Example 3, it can be seen that the charge-discharge cycle efficiency is lower than that of the Examples because LiPF6, a lithium salt with high resistance, is used alone at a slightly higher content.

[0194] In the battery cells of Comparative Examples 4 and 5, the initial performance was excellent due to the inclusion of LiN(SO2F)2, which can cause corrosion of the electrode tabs, as the lithium salt for the gel electrolyte. However, as the charge-discharge cycles progressed, the electrode tabs began to break, and the life evaluation was terminated after 100 cycles. In particular, it was confirmed that the battery cell of Comparative Example 4, which contained a higher content of LiN(SO2F)2 in the electrolyte, experienced tab breakage more quickly than the battery cell of Comparative Example 5.

[0195] Experimental Example 4: Evaluation of high temperature stability (hot box test) The battery cells manufactured in Examples 1 to 5 and the battery cells manufactured in Comparative Examples 1 to 5 were fully charged to a SOC (State Of Charge) of 100%, and the fully charged battery cells were stored in a box. The temperature inside the box was raised from room temperature to 150°C in 2°C increments, and then the cells were stored at 150°C for 120 minutes. After checking whether the battery cells had ignited during storage, the number of battery cells that ignited out of the five battery cells is shown in Table 4 below.

[0196] Experimental Example 5: Evaluation of electrode tab durability The battery cells manufactured in Examples 1 to 5 and the battery cells manufactured in Comparative Examples 1 to 5 were fully charged to a SOC (State of Charge) of 100%, and the fully charged battery cells were stored in a hot box at 60°C for two weeks, after which the battery cells were disassembled to check whether the positive electrode tabs (aluminum thin film) had broken. If even one of the positive electrode tabs of the battery cell had broken, the battery cell was classified as having a broken positive electrode tab. The experimental results are shown in Table 4 below.

[0197] [Table 4]

[0198] Referring to Table 4, it was confirmed that in the battery cells of Examples 2 to 4 of the present invention, no battery cells caught fire during the high temperature stability evaluation, and no breakage of the electrode tabs occurred.

[0199] On the other hand, in the case of the battery cell of Example 1, it was confirmed that the absence of LiN(SO2F)2, which can improve high-temperature stability, caused some fires, and in the case of the battery cell of Example 5, it was confirmed that the liquid electrolyte penetrated into the tab area, causing some disconnection of the tab.

[0200] On the other hand, in the case of the battery cells of Comparative Examples 1 to 3, the gel electrolyte does not contain LiN(SO2F)2, which induces corrosion of the electrode tabs, so the electrode tabs do not break. However, it can be confirmed that the absence of LiN(SO2F)2, which can improve high-temperature stability, causes fires in most cases.

[0201] In the case of the battery cells of Comparative Examples 4 and 5, it can be confirmed that the gel electrolyte contains LiN(SO2F)2, which induces corrosion of the electrode tabs, and therefore breakage of the electrode tabs occurs in most cases.

[0202] Although the embodiments have been described above with limited drawings, those skilled in the art can apply various technical modifications and variations based on the above, for example, the described techniques may be performed in a different order than described, and / or the components of the described systems, structures, devices, circuits, etc. may be combined or combined in a different manner than described, or may be substituted or replaced by other components or equivalents, and still achieve suitable results. Accordingly, other embodiments, examples, and equivalents of the claims are within the scope of the following claims. [Explanation of symbols]

[0203] 100: Battery cell 1000: Battery module 110: Cell case 110p1, 110p2: storage space, injection space 113: Cut-off section 114, 114T, 114P: Pouch, 1st cell sheet, 2nd cell sheet 114a, 114b, 114c, 114d: first outer circumference, second outer circumference, third outer circumference, fourth outer circumference 120, 122, 122p, 122n, 170: electrode assembly, electrode, positive electrode, negative electrode, separator 120a, 120b, 120c, 120d: first side, second side, third side, fourth side 121, 121a, 121b: electrode tab, positive electrode tab, negative electrode tab 130, 130a, 130b: electrode lead, positive electrode lead, negative electrode lead 140: Insulating film 111: Seal part 150: Gel electrolyte 155: Gel electrolyte composition 160:Liquid electrolyte 210: Fixture 211, 212, 213: Receiving base, first jig plate, second jig plate 214, 214a, 214b: First support, column, connection part 215, 215a, 215b: Second support, column, connection part X: Interface 123: Passivation film 124:Natural oxide film

Claims

1. a cell case having a storage space; an electrode assembly accommodated in the accommodating space, the electrode assembly including a plurality of electrodes, electrode tabs formed on at least one side of each of the plurality of electrodes, and separators interposed between the plurality of electrodes; a gel electrolyte containing a first lithium salt having a first molar concentration and accommodated in the accommodation space surrounding the electrode tab; a liquid electrolyte contained between the plurality of electrodes, the liquid electrolyte including a second lithium salt at a second molar concentration lower than the first molar concentration; including a battery cell.

2. The battery cell according to claim 1 , further comprising a passivation film formed at an interface between the electrode tab and the gel electrolyte by combining a first lithium salt with a cation of the electrode tab.

3. The passivation film is made of AlF ３ 3. The battery cell of claim 2, comprising at least one of LiF and LiF.

4. The battery cell of claim 1 , wherein the first lithium salt and the second lithium salt are the same or different.

5. The first lithium salt is LiPF ６ and LiBF ４ and The second lithium salt is LiPF ６ , LiFSI, LiTFSI, and LiBOB.

6. The second lithium salt is a mixture of at least one of LiFSI, LiTFSI, and LiBOB, and LiPF ６ The battery cell of claim 5 , comprising:

7. 2. The battery cell of claim 1, wherein the second molar concentration of the second lithium salt is at least 0.1 M lower than the first molar concentration of the first lithium salt.

8. the first molar concentration of the first lithium salt is 0.6 M to 5.0 M; 2. The battery cell of claim 1, wherein the second molar concentration of the second lithium salt is 0.5M to 2.0M.

9. 2. The battery cell according to claim 1, wherein a concentration ratio of the second molar concentration of the second lithium salt to the first molar concentration of the first lithium salt is 1:1.3 to 1:

5.

10. 2. The battery cell according to claim 1, wherein the gel electrolyte and the liquid electrolyte are arranged to be in contact with each other, and a first lithium salt contained in the gel electrolyte is configured to be movable into the liquid electrolyte through an interface between the gel electrolyte and the liquid electrolyte.

11. 2. The battery cell of claim 1, wherein the gel electrolyte is located only on one side of the electrode assembly where the electrode tabs are formed in the receiving space to prevent the electrode tabs inside the battery cell from moving or deforming due to an external impact.

12. The battery cell according to claim 11 , wherein the liquid electrolyte is configured to surround the other side of the electrode assembly on which the gel electrolyte is not formed.

13. A battery module comprising at least one battery cell according to any one of claims 1 to 12.

14. preparing an electrode assembly including a plurality of electrodes, electrode tabs formed on at least one side of each of the plurality of electrodes, and separators interposed between the plurality of electrodes; placing the electrode assembly in an accommodating space of a cell case; a gel electrolyte composition including a first lithium salt having a first molar concentration and a curable compound is injected into the receiving space, and then the gel electrolyte composition is disposed around the electrode tab; curing the gel electrolyte composition to form a gel electrolyte surrounding the electrode tabs; injecting a liquid electrolyte containing a second lithium salt at a second molar concentration so as to be contained between the plurality of electrodes; A method for manufacturing a battery cell, comprising:

15. The method for manufacturing a battery cell according to claim 14 , further comprising the step of forming a barrier between the receiving space of the cell case and the injection space for the gel electrolyte composition before injecting the gel electrolyte composition.

16. The first lithium salt is LiPF ６ and LiBF ４ and The second lithium salt is LiPF ６ , LiFSI, LiTFSI, and LiBOB.

17. The method of claim 14 , wherein the second molar concentration of the second lithium salt is at least 0.1 M lower than the first molar concentration of the first lithium salt.

18. 15. The method of claim 14, wherein a concentration ratio of the second molar concentration of the second lithium salt to the first molar concentration of the first lithium salt is 1:1.3 to 1:5.

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